Etherpad

Distrust GoogleDrive? Want to ensure that you own your content? Etherpad is a free, highly customizable Open Source online editor providing collaborative editing in really real-time.

Don't be saddled with endless email streams. With Etherpad, you can collaboratively edit documents in real time. It runs in your browser and is available for Mac/Linux and Windows. Although full-featured, additional plugins are available to further customize your experience.